Hydrogenation of naphthas



y 1953 E. J. HOFFMANN ET AL 2,638,438

HYDROGENATION OF NAPHTHAS Filed Sept. 1, 1950 Feed Nophfha Hydrogen IHydrogenation Zone Organic Sulfur 2 Compound 19 Treafed Naphfha .26

-Sefflin Zone Lg a g 26 Used Sodi Sodium Hydroxide Hydroxide SolutionINVENTOR. Edward J. Hoffmann, BY Edward F. WadIey,

Patented May 12, 1953 HYDROGENATION OF'NAPHTHAS v l'idward J. Hoffmanand Edward F. Wadley,

Baytown, Tex assignors, by mes'nc assigm ments; to Standard OilDevelopment Company, Elizabeth, N J., a corporation of DelawareApplication September 1, 1950, Serial No. 182,649

(01. ice-28) Claims.

The present invention is directed to a method for nydrogenating anaphtha fraction containing olefins. More particularly, the invention isconcerned with a method for hydrogenating a cracked naphtha containingmonoand diolenns under conditions such that the diolefins-areselectively hydrogenated.

The present invention involves hydrogenating a'naphtha fraction, such'asa cracked naphtha, boiling in the gasoline range containingmonoand-diolefi-ns in which the cracked naphtha has added to ita smallamount, in the range from 0.1% to 1.0% by weight, of a caustic solubleorganic sulfur compound following which the naphtha; to which thecaustic soluble organic sulfur compound is added, is contacted underhydrogenation conditions with a sulfur insensitive hydrogenationcatalyst in the presence of hydrogen to cause-selective hydrogenation ofsaid dfolefins to the substantial exclusion of the hydrogenationof themono-olefins to form a hydrogenated product containing the residualorganic sulfur compound and hydrogenated products of the suifurcompounds. The hydrogenated prodnet is then subjected to treatment Wlthasolutionof alkali metal hydroxide to remove the 'residual organic sulfurcompound and hydrogenate dproducts of sulfurand'flnally the sci-treatedfraction is recovered for further use as may be desired.

The caustic soluble organic sulfur compound may be selected from theclassconsisting: of'the aliphatic mercaptanshaving from 1 to 4 carbonatoms in the moleculeand the thiophenols boiling up to 450 F.,the'aliphatic mercaptans includingmethyl mercaptan, ethyl mercaptan,normal propyl and is'opropyl mercaptans, normal butyl, secondary butyland tertiary butylmercaptansas well as the corresponding aliphaticunsaturated mercaptans, such as ethylene merc'aptan, propylene mercaptanand the butylene mercaptans. By the term thiophenols we mean to includethe broad class of thiophenols which include benzenethiol and the alkylsubstituted benzene thiolsboiling upto 450 F. This class oi compounds,which is alsocaustic soluble, includes benzene thicl, the methyl benzenethiols, the ethyl benzene thiols, 2,4 dimethyl-l'benzene thiol, 2,5dimethyl-l benzenethiol and 23,6 trimethyldbenzene thiol.

, Organic sulfur compounds selected from the aforementioned class may beadded to the naphtha-containing mono-olefins' and diolefins iii-anamount inv the range between 0.1. and 1% by weight based on. thenaphtha.

Ordinarily the ,2 amount added may be in the range from about 6.1% to0'.5% by weight.

The hydrogenation conditions employedin'the practice of the presentinvention include the employment of a sulfur insensitive catalyst,suchas a catalyst illustrated by the sulfides of molybdenum, tungstenand nickel. Mixtures of 'the'sulholes of these metals may suitably beemployed; For example, a mixture of nickel and tungsten sulfide performsadmirably in the process'ofthe present invention.

Temperatures employed in the present invention may range from 400t0 600F. with a preferred temperature being in the neighborhood of about 500F. The pressure may be in the range from 50 =to50'0 p. s. i. g. or asomewhat lower pressure may be used; for example, apressure ores p. s.i. gsmay'be employed.

Hydrogen to oil ratio may range from to 2000 cu. ft. of hydrogen perbarrel of ieedwith good results being obtained in the range from about100' to 1000 cu. ft. per barrel. The cracked naphtha to which theorganic sulfur compound has been added may be charged in contact withthe catalyst at a liquid space velocity in the range from 1.5 to 12v./v./hour with satisfactory results being obtained in the rangefromabout 2 to 8 v./v./hour.

The invention will be further illustratedby reference to the drawing inwhich the single figure is aflow diagram of a preferred'modcoiconducting the invention.

- Referring now to the drawing, numeral l'l designates a charge tank inwhich a cracked naphthe fraction, such. as a thermallycracked'orcatalytically cracked naphtha, is stored. Such a naphthafraction may contain monoand diolcfins and may have a bromine numberany-- where from about '10 to 50 or more, depending on the content ofthe oleflnic and p'araffinie hydrocarbons therein. The feed naphtha iswithdrawn from tank H by line i2 containing pump I3 and isdischarged-thereby into a hydrogenationzone l4. Prior to entrance intohydrogenation zone Hi, the cracked naphtha has admixed with it an;organic sulfur compound which is introduced into line I2 by line 15 fromasource not shown. The caustic soluble organic sulfur compound isselected from the class of compounds illustrated but, vfor purposes ofthis description, will be assumed to'be a relatively low boilingmercaptan, such as methyl, ethyl oributyl mercaptans. The organicsulfurcompound is admixed with the cracked naphtha in: anamotmt'initherangezfrom 0.1 to 1% by weight and the admixture of naphthaand mercaptans discharged into hydrogenation zone I4 where the naphthais contacted with hydrogen introduced by line I6. For purposes of thisdescription hydrogenation zone I4 is shown as a rectangle in the drawingbut it will be clearly understood that zone I4 will include catalyticreactors containing a sulfur insensitive hydrogenation catalyst asdescribed, and means for admixing hydrogen with the naptha andseparating unreacted hydrogen and light gases which may be formed in thereaction from the hydrogenated product. Hydrogenation zone l4 may besaid to include all auxiliary hydrogenation facilities well known to theart for hydrogenating naphtha fractions containing olefins.

The conditions in hydrogenation zone I4 embrace those mentioned before.The hydrogenated product is discharged from hydrogenation zone I4 byline I! and the product will be substantially free of diolefins whilethe mono-olefins and the organic sulfur compound added to the said.naphtha may be substantially untouched. The hydrogenation product willalso include hydrogenated sulfur compounds resulting from thehydrogenation of certain sulfur compounds which may originally bepresent in the said naphtha. It is well known that hydrogenation willlower the sulfur content of petroleum fractions by converting certainsulfur compounds to hydrogen sulfide which may be readily removed fromthe hydrogenated naphtha. The hydrogenated product is admixed in line I!with a caustic alkali solution, such as sodium hydroxide, introducedthereto by line 26. The solution of sodium hydroxide may be an aqueousor alcoholic solution of, sodium hydroxide, such as a solution in methylalcohol. Preferably the sodium hydroxide solution is an aqueous solutionof sodium, hydroxide having a Baum gravity in the range of 5 to 30. Asodium hydroxide solution having a Baum gravity in the range of 5 to 30gives very satisfactory results. The admixture of hydrogenated productand sodium hydroxide solution is discharged by line I'I into a settlingzone I8 wherein a sufficient residence time is provided to allowseparation of the sodium hydroxide treated naphtha from the sodiumhydroxide solution, the treated naphtha being withdrawn by line i9 fordistillation or for further treatment, as desired, and/or for use as afuel. The used sodium hydroxide solution is discharged from settlingzone 58 by line 20, controlled by valve 2I and may be discharged fromthe system thereby. Preferably, however, a substantial portion of theused sodium hydroxide solution is recycled to line H by branch line 22controlled by valve 23 and containing pump 24 by discharging a certainamount of the used sodium hydroxide solution by manipulation of valve 2|and by introducing a suiiicient amount of fresh sodium hydroxidesolution by line 20 controlled by valve 25 to maintain the strength ofthe sodium hydroxide solution at the desired level to remove the organicsulfur compound added to line I2 by lines I5 and also to removehydrogenated products of sulfur which may be found in the productissuing from hydrogenation zone 14.

From the foregoing description taken with the drawing it will be seenthat a simple, readily adaptable process is provided for selectivelyhydrogenating diolefins in olefin-containing fractions.

The invention will be further illustrated by the following runs in whicha thermally cracked naphtha having an original sulfur content of 0.04had added to it a sufficient amount of tertiary butyl mercaptan (acaustic soluble compound) and a caustic insoluble sulfur compound toprovide a feed mixture having a lamp sulfur content of 0.25% by weight.The said naphtha had a bromine number of 41.6. A portion of the naphthato which the tertiary butyl mercaptan was added was then hydrogenated bypassing it in contact with a nickel sulfide-tungsten sulfide catalyst ata space velocity of 2.9 v./v./hour, a temperature of 505 F., a pressureof 45 p. s. i. g. and a hydrogen rate of 900 cu. ft. per barrel of feed.The hydrogenated product had a sulfur content of 0.043 of which theremaining tertiary butyl mercaptan content may be easily removed bycontact with an aqueous solution of sodium hydroxide. The bromine numberof the hydrogenated product was 33.9 while the bromine number conversionwas only 18.5%. On the other hand, the conversion of dlolefins asindicated by an ultraviolet absorption coefiicient at a light wavelength of 235 millimicrons 88%. These results clearly show that thediolefins were substantially hydrogenated to the substantial exclusionof the mono-olefins. The sulfur conversion was 83%.

A second run was made under substantially the same conditions as thefirst run with the exception that the liquid space velocity was 6v./v./hour and the hydrogen rate per barrel of feed was cu. ft. In thisinstance the sulfur content of the feed was reduced to 0.061, thebromine number to 37.4. The bromine number conversion was 10.1% whilethe sulfur conversion was 76%. Again the ultraviolet absorptioncoefficient at a light wave length of 235 millimicrons showed thatnearly 70% of the diolefins had been converted while the bromine numbershowed that only a slight amount of conversion of the mono-olefins hadbeen effected. It will be seen from the second run that at the higherspace velocities with less hydrogen substantial conversion of diolefinsto the substantial exclusion of hydrogenation of mono-olefms was effected.

A cracked naptha fraction treated in accordance with the presentinvention wherein the diolefins are selectively hydrogenated and themono-olefins are substantially unaffected is an important tool inpetroleum refining operations since the mono-olefins are very beneficialin gasoline due to their high octane numbers. On the other hand, thediolefins are very deleterious due to their inherent characteristics ofreacting with oxygen and forming gum compounds. Therefore, the presentinvention, which selectively removes the diolefins, removes thedeleterious compounds without afiecting the beneficial compounds byincorporating in the feed stock to a hydrogenation process an amount ofan organic sulfur compound which is caustic soluble and which may beremoved from the hydrogenation products. It is only the caustic solubleorganic sulfur compounds which may be effectively employed in thepractice of the present invention and removed therefrom in accordancewith the aforementioned description.

The nature and objects of the present invention having been completelydescribed and illustrated, what we wish to claim as new and useful andto secure by Letters Patent is:

l. A method for hydrogenating a naphtha fraction boiling in the gasolinerange containing monoand diolefins wherein the diolefins arehydrogenated selectively which comprises adding to said naphtha fractiona caustic soluble organic sulfur compound selected from the classconsisting of the aliphatic mercaptans having from 1 to 4 carbon atomsin the molecule and the thiophenols boiling up to 450 F. in an amount inthe range from 0.1% to 1.0% by weight based on said naphtha, contactingthe naphtha to which the organic sulfur compound has been added with asulfur insensitive hydrogenation catalyst at a temperature in the rangebetween 400 and 600 F. and at a pressure between45 and 500 p. s. i. g.in the presence of hydrogen under conditions to cause selectivehydrogenation of said diolefins to the substantial exclusion ofhydrogenation of said mono-olefins to form a hydrogenated productcontaining said organic sulfur compound and hydrogenated products ofsulfur, treating said hydrogenated product with a solution of alkalimetal hydroxide to remove therefrom said organic sulfur compound andhydrogenated products of sulfur and recovering said treated product.

2. A method for hydrogenating a cracked naphtha fraction boiling in thegasoline boiling range containing monoand di-olefins wherein thediolefins are selectively hydrogenated which comprises adding to saidnaphtha fraction a caustic soluble organic sulfur compound selected fromthe class consisting of the aliphatic mercaptans having from 1 to 4carbon atoms in the molecule and the thiophenols boiling up to 450 F. inan amount in the range from 0.1% to 1.0% by weight based on saidnaphtha, contacting the naphtha to which the organic sulfur compound hasbeen added with a sulfur insensitive hydrogenation catalyst at atemperature in the range between 400 and 600 F. and at a pressure in therange between 45 and 500 p. s. i. g. in the presence of 100 to 2000cubic feet of hydrogen per barrel of said naphtha fraction at a liquidspace velocity in the range of 1.5 to 12 v./v./hour to cause selectivehydrogenation of said diolefins to the substantial exclusion ofhydrogenation of the mono-olefins to form a hydrogenated productcontaining said organic sulfur compound and hydrogenation products ofsulfur, treating said hydrogenated product with an aqueous solution ofan alkali metal hydroxide to remove therefrom said organic sulfurcompound and hydrogenated products of sulfur and recovering said treatedproduct.

3. A method in accordance with claim 2 in which the solution of alkalimetal hydroxide is an aqueous solution of sodium hydroxide.

4. A method for hydrogenating a cracked naphtha fraction boiling in thegasoline boiling range containing monoand diolefins wherein thediolefins are hydrogenated selectively which comprises adding to saidnaphtha fraction a caustic soluble organic sulfur compound selected fromthe class consisting of methyl mercaptan, ethyl mercaptan, the propylmercaptans, the butyl mercaptans, benzene thiol, the methyl benzenethiols, the ethyl benzene thiols, 2,4 dimethyl- 1 benzene thiol, 2,5dimethyl-l benzene thiol and 2,4,6 trimethyl-l benzene thiol, in anamount in the range from 0.1% to 1.0% by weight based on said naphtha,contacting the naphtha to which the organic sulfur compound has beenadded with a sulfur insensitive hydrogenation catalyst at a temperaturein the range between 400 and 600 F. and at a pressure between 45 and 500p. s. i. g. in the presence of hydrogen under conditions to causeselective hydrogenation of said diolefins to the substantial exclusionof hydrogenation of said mono-olefins to form a hydrogenated productcontaining said organic sulfur compound and hydrogenated products ofsulfur, contacting said hydrogenated product with a solution of sodiumhydroxide to remove therefrom said organic sulfur compound andhydrogenated products of sulfur and recovering said treated product.

5. A method for hydrogenating a cracked naphtha fraction boiling in thegasoline boiling range containing monoand diolefins which 7 comprisesadding to said naphtha fraction a caustic soluble organic sulfurcompound selected from the class consisting of methyl mercaptan, ethylmercaptan, the propyl mercaptans, the butyl mercaptans, benzene thiol,the methyl benzene thiols, the ethyl benzene thiols, 2,4 dimethyl- 1benzene thiol, 2,5 dimethyl-l benzene thiol and 2,4,6 trimethyl-lbenzene thiol, in an amount in the range from 0.1% to 1.0% by weightbased on said naphtha, contacting the naphtha to which the organicsulfur compound has been added with a nickel-tungsten sulfidehydrogenation catalyst at a temperature in the range between 450 and 550F. and at a pressure between and 500 p. s. i. g. in the presence ofhydrogen under conditions to cause selective hydrogenation of saiddiolefins to the substantial exclusion of hydrogenation of saidmono-olefins to form a hydrogenated product containing said organicsulfur compound and hydrogenated products of sulfur, contacting saidhydrogenated product with an aqueous solution of sodium hydroxide toremove therefrom said organic sulfur compound I and hydrogenatedproducts of sulfur and recov- Name Date 2,143,078 Lyman et a1. Jan. 10,1939 2,367,348 Harrington Jan. 16, 1945 2,392,579 Cole Jan. 8, 19462,413,312 Cole Dec. 31, 1946 2,511,453 Barry June 13, 1950

1. A METHOD FOR HYDROGENATING A NAPHTHA FRACTION BOILING IN THE GASOLINERANGE CONTAINING MONO- AND DIOLEFINS WHEREIN THE DIOLEFINS AREHYDROGENATED SELECTIVELY WHICH COMPRISES ADDING TO SAID NAPHTHA FRACTIONA CAUSTIC SOLUBLE ORGANIC SULFUR COMPOUND SELECTED FROM THE CLASSCONSISTING OF THE ALIPHATIC MERCAPTANS HAVING FROM 1 TO 4 CARBON ATOMSIN THE MOLECULE AND THE THIOPHENOLS BOILING UP TO 450* F. IN AN AMOUNTIN THE RANGE FROM 0.1% TO 1.0% BY WEIGHT BASED ON SAID NAPHTHA,CONTACTING THE NAPHTHA TO WHICH THE ORGANIC SULFUR COMPOUND HAS BEENADDED WITH A SULFUR INSENSITIVE HYDROGENATION CATALYST AT A TEMPERATUREIN THE RANGE BETWEEN 400* AND 600* F. AND AT A PRESSURE BETWEEN 45 AND500 P. S. I. G. IN THE PRESENCE OF HYDROGEN UNDER CONDITIONS TO CAUSESELECTIVE HYDROGENATION OF SAID DIOLEFINS TO THE SUBSTANTIAL EXCLUSIONOF HYDROGENATION OF SAID MONO-OLEFINS TO FORM A